Objective To investigate the physiological mechanisms of drought adaptation and protective enzyme system of Saposhnikovia divaricata under drought stress.

Method Three levels of water supply including full irrigation (CK), light drought stress(LD) and severe drought stress (SD) treatments were set up for annual S. divaricata. Effects of drought stress on leaf protective enzyme activities, contents of osmoregulation substances and total content of two chromones (prim-O-glucosylcimifugin and 5-O-methylvisammioside) of S. divaricata were studied.

Result The activities of superoxyde dismutase (SOD), peroxidase (POD), catalase (CAT), and proline content under different water treatments increased during early test stage, reached peak during middle stage and then decreased. Malondialdehyde (MDA) content under different water treatments increased throughout the entire test period. The total contents of two chromones under different water treatments all increased at early stage, reached peak during middle stage and then decreased for LD and SD treatments, while slowly increased during both middle and late stage for CK treatment. Changes in the activities of SOD, POD and CAT, the contents of osmoregulation substances, and the total contents of two chromones for LD and SD treatments were higher compared to CK, and the peak values of these measurements for LD and SD treatments were also higher compared to CK. There were significant correlations between CAT activity, the total content of two chromones and SOD activity under different water treatments.

Conclusion Appropriately imposing drought stress in the cultivation of S. divaricata can increase protective enzyme activities and the contents of osmoregulation substances of S. divaricata leaves, which is beneficial for S. divaricata growth and can increase the total content of two chromones.